Lime and phosphogypsum in long-term no-till: soil quality improving crop physiology and 15N-fertilizer recovery in the soil-plant system

Author(s)

João WIlliam Bossolani

• Document type: Doctoral Thesis
• Press: Botucatu. 2022-08-17.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agronômicas. Botucatu
• Defense date: 2022-06-28
• Advisor: Carlos Alexandre Costa Crusciol; Nídia Raquel Costa

Abstract

The present study is part of a long-term experiment, started in 2002, at Fazenda Experimental Lageado, belonging to the College of Agricultural Sciences (UNESP/FCA), in Botucatu (SP). Continuing the experiment, which is likely to be the only one in the State of São Paulo with such a duration (19 years), the present Thesis aimed to understand the effect of long-term surface application of lime and phosphogypsum on the soil chemical and biological attributes, root growth, plant nutrition, carbon e antioxidant metabolism, 15N-fertilizer recovery in the soil-plant system, and yield of maize intercropped with ruzigrass and soybean in succession. The field part of this study has been carried out since October 2016, when lime and/or phosphogypsum were last applied. Therefore, here we tested the following treatments: i) control (no soil amendments applied), ii) phosphogypsum alone, iii) lime alone and, iv) lime and phosphogypsum combination. Soybean sowing occurred between November and December of each year, whereas maize intercropped with ruzigrass was sown in March of each year. Our results suggested that the combination of lime and phosphogypsum proved to be effective in improving soil fertility up to 1 m depth, reflecting ideal conditions for root growth of soybean and maize intercropped with ruzigrass. As a result of these changes, crop nutrition was also improved, ensuring high photosynthetic metabolism even when periods of water scarcity occurred. In the combined application of lime and phosphogypsum, antioxidant metabolism based on free radical-consuming enzymes also increased, reducing lipid peroxidation of leaf cells. This cascading effect was reflected in the increase in grain yield of both crops. Deepening the understanding of tropical agricultural systems altered by the application of lime and phosphogypsum, our microbiological studies revealed that the joint application of lime and phosphogypsum altered the soil chemical properties in a no-till intercropped system, increasing the relative abundance of total prokaryotes (archaea and bacteria), modulating genes related to the nitrogen cycle. Finally, our results also revealed that the combined application of these inputs increases the recovery of 15N fertilizer [(15NH4)2SO4] by maize and ruzigrass in intercropping, and soybean cultivated in crop rotation, which reduced N losses to the environment. Our study highlighted the importance of using soil amendments in tropical agricultural systems, mainly in exploring the synergistic effect of lime with phosphogypsum, aiming to improve the soil chemical and microbiological quality, the nitrogen fertilizer recovery, the photosynthetic and antioxidant metabolism of plants and, consequently, the grain yield of the crops. (AU)

• FAPESP's process: 18/11063-7 - Lime and phosphogypsum in long-term no-till: soil quality improving crop physiology and 15N-fertilizer recovery in the soil-plant system
• Grantee: João William Bossolani
• Support Opportunities: Scholarships in Brazil - Doctorate